Energy and fuels are essential in modern life. Most widely used type of fuels are fossil fuels. Fossil fuels, including coal, are essentially hydrocarbons containing carbon and hydrogen in various ratios.
Coal, like any carbon-containing fuel, forms carbon dioxide upon its combustion, and therefore is not renewable on the human timescale. Also, because carbon dioxide is a greenhouse gas, combustion of coal contributes to global warming. Although clean coal technology has been developed as a solution to continued use of coal resources, it is so far directed only at reducing harmful pollutants such as sulfur oxides, nitrogen oxides and heavy metals formed from burning coal and does not address carbon dioxide emission. It has been suggested to mitigate harmful carbon dioxide emissions by imposing carbon quota or by capturing carbon dioxide emissions and sequestering it underground or at the bottom of the sea. Sequestration, however, is a costly and only a temporary solution that presents a risk that sequestered carbon dioxide may be released abruptly with deadly catastrophic consequences in the event of geological events such as earthquakes and slides.
Thus, it would be desirable to make coal use environment-friendly and at the same time regenerative by capturing and chemically recycling carbon dioxide emissions to useful fuels and derived products.